One example of such a down-light includes a light source block, a lighting circuit block, a mounting board and a terminal block assembled in a housing, wherein a frame is mounted to a bottom opening for emitting light (see, e.g., Japanese laid-open patent application JP2006-172895A, paragraphs 0020-0030, FIGS. 1-7).
In such a down-light, a mounting board is provided horizontally in the housing. A lighting circuit block and a terminal block are mounted on the upper surface of the mounting board. Further a light source block is mounted on the lower surface of the mounting board. The light source block comprises a printed circuit board on which a plurality of LEDs are mounted, and a lens system for controlling spatial distribution of luminous intensity of light emitted from the LEDs. The lens system is formed in a thin cylindrical shape by light-transmissive material. The lens system is provided with a space for accommodating a printed circuit board on which a depression is formed on its upper side for arranging each LED. The frame comprises a cylindrical side wall whose diameter gradually expands from top to bottom and a flange provided at the bottom portion of the frame. The flange is so formed to hang over a brim portion of the housing and catch on a lip of the ceiling recess. The inner surface of the side wall serves as a reflective surface for guiding downward light transmitted through the lens system from the light source block and introduced into the cylindrical side wall.
In the down-light disclosed in the prior art JP2006-172895A, the light emitting surface of the lens system which controls luminous intensity distribution of the light emitted from the LED is horizontally disposed at the level closing the upper opening of the frame. As a result, the entire region shines brightly. As a result, the light source block itself fails to achieve a desirable light shielding angle.
In order to counteract the disadvantage in the down-light disclosed in the prior art JP2006-172895A, the lens system may be directly allocated beneath the housing by removing the frame which undesirably reflects the light from the light source block. However, there occurs in such a modification another problem that since the luminosity of the LED itself is extremely high, a dazzle feeling of the light source block becomes strongly conspicuous. In a down-light, wherein the frame is allocated beneath the light source block like the down-light disclosed in the prior art JP2006-172895A, a certain degree of light shielding angle can be ensured by a frame. However, for enlarging the light shielding angle further, the height of the frame must be increased. When the height of the frame is increased, there occurs still another problem that the downright illumination zone obtained by reflection on the frame becomes narrower.
Further, the lens system provided in the down-light disclosed in the prior art JP2006-172895A is formed to have a total-internal-reflection surface for effectively utilizing the light from the LED. A lens system having such a total-internal-reflection surface must have a thickness larger than a certain amount. Therefore, in the manufacturing of the lens system, a molding tact time becomes long. As a result, the manufacture efficiency is insufficient and thus the manufacturing of the lens system is costly.